1. Field of Invention
The present invention relates to the field of fuel gas combustion, and more particularly but not by way of limitation, to an improved compact hi-spin gas burner which is inexpensive to construct, efficient to operate, modular in construction and effective in performance while yielding favorable emission ratings, and which achieves unrestricted spatial orientation.
2. Discussion
Power burners, those that utilize a prime mover to force all the combustion air into the combustion zone, are divided into two main classes: diffusion burners and premixed burners. Diffusion burners keep the air and fuel separate until the point of ignition. Under these conditions, the rate of reaction is faster than the rate of diffusion because the physical mixing of the reactants, the fuel and the air, is slower than the chemical rate of reaction. These factors, that is, the relatively slow rate of combustion and the maintained separation of the reactants until reaching the point of ignition, significantly reduce the dangers of flash back within the burner. However, the flames in diffusion burners are heterogeneous with respect to the reactants, to the products of combustion, and to the temperature gradients, thereby resulting in a long and yellowish flame that can comprise of large amounts of NOx.
Premixed burners produce homogeneous flames, i.e., uniform in temperature and products of combustion, because the uniform premixing of the fuel and gas before the point of ignition increases the reaction rate and creates a short and relatively blue flame. The uniformity in temperature creates a flame that has reduced NOx emissions. However, the presence of a combustible mixture throughout the burner tube can result in an increased chance of flashback whereby the flame travels back in the mixture tube, possibly resulting in an explosion or extreme damage to the burner equipment.
With regard to NOx emissions, the United States Environmental Protection Agency (EPA) was established to regulate air quality at a national level. At the EPA's recommendation, Congress passed the Clean Air Act Amendments to identify the processes producing pollutants and to impose pollutant emission limits on the States in an effort to establish air quality standards.
The Combustion industry was made a regulatory target for mandated control of nitrogen oxide and carbon monoxide emissions. Combustion of fossil fuels generates air pollutants including oxides of both carbon and nitrogen. In particular, boilers and steam generators, commonly used in industrial and commercial applications, burn fuel with air to produce heat, and thus also produce significant amounts of pollutants, including oxides of carbon and nitrogen. Oxides of nitrogen, collectively known as NOx, are major air-borne pollutants that can potentially cause acid rain, ozone destruction, global warming, smog formation, and vegetation destruction. Emission of carbon monoxide, CO, is not only harmful to the environment, but also is an indicator of low combustion efficiency, as CO is the product of partial combustion.
In anticipation of regulatory control, a continuing trend in the combustion industry has been the development of boilers that produce lower NOx and CO emissions, and this at ever decreasing costs. To this end, improvements are continually being made to improve the efficiency of combustion in boilers while reducing deleterious emissions.
The prior art includes a variety of approaches to minimizing NOx emission rates, including both external and internal flue gas recirculation (FGR); steam injection (SI); fuel and air staging; premixing; controlled excess air firing; ceramic fiber; selective catalytic and non-catalytic reduction (SCR and SNCR); low NOx oil (for oil burning); and methods to introduce instabilities in the flow field, including the use of elliptical geometries, resonant generators, etc. However, these methods vary in cost as well as effectiveness in the reduction of NOx, and expensive components are necessary for implementing these methods. Further, as most power burners are designed for a particular type of boiler, water heater, or steam generator, each such prior art method of reducing NOx is generally application specific, limiting the usefulness of the prior art burners.
Accordingly, there is a continued need for burners that produce homogeneous flames with reduced NOx while avoiding the dangers of flashback. Also, it is desirable that such burners achieve increased efficiency of combustion and versatility of application, and that such burners be capable of being produced economically.